Human immunodeficiency virus-infected and immune competent brain mononuclear phagocytes (MP; macrophages and microglia) secrete cellular and viral toxins that affect neuronal damage during advanced disease. Methamphetamine (METH) abuse causes even more significant neuronal aberrations and the changes can be associated with impaired cognitive functions, such as learning, problem solving, and processing information. Together METH abuse and HIV infection appears to result in greater impairment than each condition alone. Amongst a number of cues and host cell immune factors that can control such events, astrocytes affect such disease processes and the cells abilities to modulate the nervous system's microenvironment. Interestingly, little is known how astrocytes communicate with MP to curtail disease and notably in the setting of METH abuse. Thus, this project will investigate MP-astrocyte crosstalk using state of the art biological analysis coupled with proteomic fingerprint tests. The microglial-astrocyte dialogue will be evaluated in the setting of METH for how abused drugs can affect microglial functions and affect astrocyte regulation of neurotoxicity. Specifically, a complete proteomic analysis will be done including the cytoskeleton, cell death, and migratory pathways linked to specific biological outcomes. How such glial crosstalk is mediated will be uncovered with a focus on microglial affected viral growth. These processes are known to be linked to the regulation of reactive oxygen species and other disease-modulatory factors in cell and rodent models of human disease. These experimental results will be joined with projects 2 and 3 (Drs. Fox and Ciborowski) so that studies at the cellular level can be sought in relationship to focused animal model experimentation and clinical endpoints. The public health relevance of this work is that combined toxicity of HIV and METH on the brain can result in substantial problems for those who are HIV infected and abuse METH. This research will uncover the basis of the interaction of these agents on brain cells, leading to information that can be disseminated to dissuade METH use, and provide targets for potential therapeutic intervention.